This invention relates to a gas filled cylinder of the type composed of two concentric tubes separated by a chamber and also separated by a valve plug and a shaft plug, arranged inside the outer tube and against which the inner tube is seated,
A valve shaft passes through the valve plug, which, with its movements, allows the passage of gas to the interior of the inner tube. A piston connected to a shaft moves in this space, with the piston moving, together with the said shaft, according to the movement in question, and with the gas passing from one space to the other according to the direction of this movement.
Examples of cylinders of this type are known through FR-A-2661229 and EP-A-0634587. In these references and especially in the second one mentioned, the valve plug consists of two parts assembled together, between which the gradual passage of the gas is created towards the chamber between the tubes, while also forming an annular space in which a ring seal or sealing ring is arranged that makes contact with the interior of the outer tube for sealing purposes.
The two components of the valve plug make frontal contact with each other and it is the upper one which is provided with an annular slot for the sealing ring. In turn, this upper component receives at its top a washer which is supported on it, with an inner body of the cylinder itself being supported on this washer.
The cylinder shaft is a single part that includes the piston. This unit is produced by machining and a leaktight ring seal is later fitted to the head or piston.
In these techniques, there is the disadvantage that the leaktightness provided by the ring seal arranged between the two components of the valve plug is not as satisfactory as would be expected, given that the ring seal is not subjected to any flattening or pressure in order to act suitable against the wall of the outer tube.
Moreover, other disadvantages of known shafts of this type lie fundamentally in the need to carry out machining of a certain complexity and, of course, at a cost which is not insignificant.
One object of the invention is to provide a valve plug of he type described that provides a greater leak-tightness or sealing capacity of the plug and therefore greater safety in operation.
Another object of the invention is to provide a valve plug that lightens its weight.
Another object of the invention is to provide a valve plug that does not alter the cost of the manufactured product arid which, in addition, preserves and increases the service life of the components.
Another basic object of the invention is to provide a shaft for cylinders of this type that considerably reduces the machining.
Another object of the invention is to provide a shaft for gas filled cylinders that requires only simple to perform machining and is without any kind of technical complexity.
Finally, another object of the invention is to provide a shaft that is noticeably cheaper than conventional ones.
In order to achieve these objectives, the invention claims a valve plug consisting of two components assembled together with a stepped space between them in order to allow the passage of gas to the space between the tubes, with the particularity that this connection between both components is without any ring seal.
The ring in this case is transferred to the upper part above the upper component of the plug and between this and the washer that receives the inner body of the cylinder.
The washer is provided with a downwardly protruding neck from its central hole, and this neck becomes housed in an annular recess made in the upper part of the valve plug.
The washer presses against the ring seal as a result of the pressure that it receives from the inner body of the cylinder, so that this pressure is transmitted directly to the seal, causing it to become flattened and the pressure to be transmitted towards the exterior, thus adjusting it perfectly to the surface of the outer cylinder at all times.
Moreover, the lower body of the valve plug is provided with a wide cylindrically shaped cavity which is open downwards and which, without any detriment to the strength of the body, eliminates material and weight from the part.
In addition, the invention also claims a shaft composed of four separately produced parts, which are respectively, a shaft itself, a washer and a conventional ring seal and a part by way of a piston head, made of plastic material or similar.
The shaft is made starting from a basic cylindrical element, one of whose ends, the one that is connected to the item to be damped and obviously protrudes towards the exterior of the cylinder, is machined in the same way as the traditional shafts mentioned previously. The opposite end is carried out by making only one area of a smaller diameter for a certain length.
At this end which has been prepared in this way, the head of the piston, a circular crown shaped part, is housed, which at the edge of its central hole has a kind of countersinking on which a small ring seal rests.
This circular crown has a flat side surface area of the same diameter as the inner tube of the cylinder, through which it slides along the said inner surface.
A washer with the same interior diameter as he reduced diameter area of the shaft is placed above the latter part (the washer), with this washer placing pressure on the previously mentioned ring seal so that it fits perfectly to the shaft. In order to ensure this pressure and the consequent leak-tightness, the portion protruding from the reduced area of the shaft is riveted over the said washer, thus fixing the assembly and forming the shaft in accordance with the invention.